Age-related cataract is the main cause of impaired vision in the elderly population worldwide. In the UK, more than half of people who are over 65 have some cataract development in one or both eyes. The only treatment that can restore functional visual ability is cataract surgery where the opacified crystalline lens is removed by phacoemulsification and an artificial intraocular lens is implanted. It is estimated that around 10 million cataract operations are performed around the world each year. Cataract operations are generally very successful, with a low risk of serious complications. The most common risk is developing a condition called posterior capsule opacification (PCO), which causes impaired vision to return.